There exists a class of devices for accessing fluid spaces and vessels within a human (or animal) body that are generally referred to as "ports". Herein, "vessel" is defined as any conduit carrying a fluid within the patient's body. These prior art devices comprise a chamber having an access opening sealed by means of a septum and having an egress from a second location leading to a catheter disposed within a fluid space or vessel. The septum allows a needle to pass into the chamber, but then closes when the needle is removed, thereby preventing fluid leakage from within a space or vessel and also anything from entering or exiting the chamber. These devices are usually implantable below the skin to prevent infection, other contamination, and mishandling.
Ports are designed for relatively infrequent use, perhaps once a week, and, importantly, for flow rates of 50 milliliters per minute or less, as is common during chemotherapeutic treatment. Modification of these devices for hemodialysis, plasmapheresis, and other fluid exchange therapies, which require much greater flow rates, by simply enlarging the device components, poses several serious drawbacks that effectively limit use in such applications. First, the septum degrades quickly due to the larger gauge needles necessary to accommodate the flow rates required in hemodialysis. Repeated puncturing of the septum by these large needles produces numerous free-floating septum fragments that can find their way into the circulatory system. Accordingly, the useful life of the devices is substantially shortened, thereby defeating one of the purposes of using an implantable subcutaneous device. Second, the flow path has several stagnation points where clots may form and also is not completely flushable or easily cleaned, thereby providing breeding grounds for infection, once contaminated or a build-up of material which may adversely affect function. Third, the flow path is not streamlined and contains flow path obstructions, sharp corners, and abrupt changes in flow area and flow direction. This tends to increase the shear stress and turbulences experienced by blood flowing through the device due to the significantly higher flow rates required in hemodialysis, thereby increasing erythrocyte damage and platelet activation. Also, the tortuous flow path increases the flow path resistance and the pressure drop through the devices, such effects can increase air release and foaming, causing the dialysis machine's safety alarms to activate.
A general limitation in all relevant prior art devices is the lack of a streamlined flow path. Without such streamlining, stagnant volumes exist where clots may form and shear stress is higher, tending towards erythrocytic damage. Such locations cannot be flushed or easily cleaned. Blood residue remaining in the devices after flushing may clot and provide breeding grounds for infection, once contaminated. In addition, pressure drops and abrupt flow direction changes may damage blood components.
The present invention is also useful for other liquid or fluid (including gases) transfer purposes into and out of human and animal bodies, including the transfer of externally prepared solutions for cleaning, flushing, dialysis, chemical agent delivery, transfusions, blood donation, insufflation, wound drainage, etc.
Accordingly, it is a principal object of this invention to overcome the above illustrated inadequacies and problems of extant devices by providing a totally implantable access means suitable for repeated use in applications (e.g., hemodialysis with blood flow rates of 250 milliliters per minute or more yet with low pressure drops along the flow path).
It is another principal object of the invention to optimize fluid flow in hemodialysis particularly and in other applications referred to generally, above.
It is another object of this invention to provide a substantially laminar flowstream
It is yet another object of this invention to minimize flow discontinuities and to substantially match the internal diameters of the injecting cannula and the receiving catheter, and a related object is to bring the exit end of the cannula and the entrance end of the catheter into close proximity.
It is a further object to provide means where the flow path is streamlined and provides substantially no stagnation points, no flow discontinuities, and also to provide an apparatus where the entire flowstream is flushable.
It is a further object to the invention to minimize internal fluid collection zones or stagnant volumes in such a device.
It is a still further object to have lower clotting, stenosis, and infection rates than synthetic grafts.
It is yet another object to have lower infection and lumen clotting than percutaneous catheters.
It is a still further object of this invention to provide apparatus suitable for single and dual-lumen catheter systems.
It is yet another object of this invention to provide an access device that is less painful during needle insertion and more accommodating during dialysis for the patient.
It is a further object of the invention to minimize irritation and other adverse effects associated with intermittent skin puncture over a course of days, months or years of repetitive access.
It is a further object to secure the needle within the access device during the dialysis session.
It is a further object of the invention to enhance the devices to more effectively lock in a cannula to the device to avoid inadvertent separation, yet allow ease of deliberate release of the cannula.
It is another object of the invention, when using dual-lumen catheters, to secure both needles to each other.
It is a further object of the invention to provide ease of manufacture and assembly of such device consistent with enhanced locking.
A further object of the invention is to establish economy of the lock devices for disposability.
It is a further object of the invention to provide enhanced cannula and obturator handling external to a patient via hub devices coordinated with the structure and functions of the locking devices.
It is also an object of the invention to accommodate multiples of the foregoing objects together.